The invention relates to a method for changing a reel in a reeling process of a fiber material web, for example in the reel-up of a paper or paperboard machine or a paper or paperboard finishing apparatus. In particular, the invention relates to a change in a continuous reel-up without reducing the running speed of the web.
In the reel-up of a paper machine, in a so-called pope reel-up or in a center drive assisted reel-up, finished paper is reeled around a reeling core, such as a reel spool, after the calender. The reeling itself is conducted in such a manner that the reeling core is loaded against a member for guiding the web, i.e. a reeling cylinder, via which the web to be reeled travels, winding around the reeling core and to form a complete reel. The reeling may take place by means of surface draw (the reeling cylinder or the like to be driven and simultaneously to rotate the reel) or a center drive (also the reeling core to be driven).
This section of the paper machine should also function without interruptions and receive the continuous paper web coming from the preceding sections of the paper machine. Thus, when the old reel has become full, it is necessary to cut the web and start to wind the web following the cutting point around a new reeling core. In practice, this takes place in such a manner that when the paper reel has become full, a new empty reeling core, i.e. for example a reel spool is transferred onto the surface of the reeling cylinder in contact with the paper web, whereafter the paper web is cut or brought to tear by means of a suitable method, and the end of the web following the cutting or tearing point is guided onto the periphery of the empty reeling core, on which the new reel now starts to accumulate.
The most critical phases in the reeling are, in fact, the cutting or tearing of the paper web running to the old reel at production speed and the act of bringing the new end of the web around the empty reeling core. To avoid unnecessary broke, the change must take place without problems. The ideal case is to bring the new end of the web immediately and neatly against the peripheral surface of the empty core, such as a reel spool, without extra loose pieces or creases of the web, because otherwise so-called bottom broke may be produced. It is well known that many methods are used for the change, depending on the grade or basis weight of the web to be reeled.
A generally used change method is pocket change which is suitable for all grades, but which typically causes quite a large amount of bottom broke and may cause harmful impacts in the reel-up. Another method is the so-called gooseneck change in which the above-mentioned problems are less severe, but which is suitable for thin grades only. A third method is the tape change, in which a tape is guided into the nip between the reeling core and the reeling cylinder in the vicinity of the ends of the reeling core and the reeling cylinder, whereafter the tape, as it winds spirally over the width of the reeling core, at the same time cuts the web diagonally and guides the new end following the cutting point of the web around the reeling core.
At present, the speeds of paper machines are generally 20 m/s or higher, and the aim is, of course, to attain even higher speeds. The cutting of a rapidly travelling web is not a problem as such, and forces caused by the speed can even be utilized in the cutting. The critical point is to bring the end of the new web immediately against the peripheral surface of the reel spool so that it follows the peripheral surface at a high peripheral speed, and to prevent the uncontrolled wandering of the end of the web and incorrect positioning of the same on the reel spool. This problem becomes worse when the basis weight is increased; in other words, greater forces must be used for “heavy” grades to overcome the inertial forces, i.e. to deflect the web from its original travel direction, which is towards the old reel.
On a continuously operating reel-up, the end of the web cannot be glued to the reeling core before the reeling begins, as is the case in reeling conducted by means of slitter winders, because when using known methods the glueing would require that the machine is stopped. In other respects, the glueing would be a secure way to pull the web around the new reeling core by means of its rotating motion. On the other hand, when applied as such, the glue acts in an uncontrolled manner, it may smear the surface of the reel spool, and it increases the need for cleaning. Furthermore, applied glues are also harmful in other respects, because some glue will adhere to the broke, and their repulpability is poor.
Changes carried out by air jets, in which it is possible to utilize a wedge or a tip cut from the web before the new reeling cylinder, or a band separated by two parallel incisions and a transverse incision by a blade in the area of the band, are presented, for example, in the patents EP 658 504, EP 765 832, U.S. Pat. No. 4,445,646, and U.S. Pat. No. 5,360,179.
U.S. Pat. No. 5,441,211 discloses a web change to a new reeling core by means of a slit in the cross direction of the web and a following adhesive area. The slit and the following adhesive area are produced in the web by a wheel placed before the change nip and equipped with a cutting edge and double-sided adhesive tape immediately following it. The transfer of the web around the new reeling core after the slit and the tearing of the web towards the edges are enhanced by a blow that takes place after the nip.
German application publication DE 2721883 also discloses a band separated in the central area of the web, to be cut after the change nip in the running direction of the web and to be blown around a new reeling core using a blade and a nozzle placed underneath the blade.
In general, the risk of a web break is involved in all the change methods in which the web running at full speed is touched before the change nip. This is the case when incisions are made by a blade or when an element, for example an adhesive piece, is attached to the web. For instance, an incision made by a blade, a “punching knife” before the change nip for the purpose of producing a slit, through which the web can be torn by blowing after the nip in the gooseneck change, is one example of such a change method involving a risk factor (for example, the gooseneck change presented as prior art in FIGS. A1 and A2 of U.S. Pat. No. 5,360,179).
The aim of the invention is to eliminate the above-mentioned drawbacks and to present a method by which the web can be brought safely around the new reeling core, without the application of a glue or without other smearing operations, or without bottom broke.